A variety of hinge devices have been proposed. A body and a flip of a portable phone or a body and a cover of a note-type personal computer are pivotally coupled by a hinge device basically having the following structure.
A cam portion is provided within a mounting case member in a rotation preventing manner. This cam portion is slidably movably provided within the mounting case member against an engagement biasing spring provided within the mounting case. A cam engagement portion to be engaged with the cam portion by the engagement biasing spring is provided in confrontation with this cam portion. This cam engagement portion is projectingly provided on one side of the mounting case member. The mounting case member is provided in a fixed condition to either the first member or the second member. When the second member is rotated to the first member, the cam portion and the cam engagement portion are disengaged from each other and rotated relative to each other while the cam portion is separated against the engagement biasing spring. Under the condition that the cam portion and the cam engagement portion are biased and engaged with each other, the rotational position of the second member may be kept to the first member.
It is therefore possible to realize a “free stop” for stopping and keeping in the rotational position under the condition that the hand is released upon the rotation in the disengagement position by, for example, the engagement spring. Also, the cam is engaged in the rotational position in which the second member is opened at a predetermined angle so that the rotational position is locked. Also, under a coupled and closed condition, the cam is on the way in engagement so that the closing bias may take place.
On the other hand, conventionally, in such a hinge device, for example, a mounting hole provided in the first member and a communication mounting hole provided in the second member are arranged in communication with each other. The hinge device is inserted from one side so that the mounting case member is fitted in the mounting hole in a rotation preventing manner and the cam engagement portion is fitted in the communication mounting hole in a rotation preventing manner. Thereafter, the hinge device is secured by screws from the outside to prevent the pull-apart.
For this reason, after the hinge device has been assembled (after it has been inserted into an assembling portion), it is necessary to fixed it with discrete parts (such as rivets or pins). Accordingly, the mounting work is troublesome and it is impossible to perform the mounting work with one action.
Accordingly, in order to overcome the above-noted problems, an object of the present invention is to provide a novel hinge device which may be mounted with one action, extremely superior in mounting work and in practical usability and an electronic instrument using the hinge device by a retractable motion and an automatic return motion without fixing the hinge device by any discrete part device while paying attention to the structure where at least one cam portions engaging with each other is slidably moved against an engagement spring, implementing such improvement that the other cam engagement portion is also moved against the spring together with the cam portion, implementing such improvement that the cam engagement portion projecting on one side of a mounting case member or a mounting portion provided on this may be retractably moved.